Area Forecast Discussion
Issued by NWS Wilmington, OH

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000 FXUS61 KILN 230720 AFDILN Area Forecast Discussion National Weather Service Wilmington OH 320 AM EDT Thu Mar 23 2017 .SYNOPSIS... Return southeast flow will allow temperatures to modify today. A warm front will push northeast through the region tonight, bringing a few showers to the area. Temperatures will continue to warm on Friday as southerly flow increases. A low pressure system over the central Plains will slowly move into the Great Lakes and Ohio Valley this weekend. Warm temperatures will continue along with an increasing threat of showers and thunderstorms. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Freeze Warning will continue for locations along and south of the Ohio River through 10 am EDT. Otherwise, surface high pressure to our east will move to the Atlantic seaboard by this evening. For our area, return surface southeast flow and developing WAA overall will allow temperatures to modify from a cold start. Also, mid and high level clouds will increase from the west through the day. Highs will range from near 50 far north to near 60 along and south of the Ohio River. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM FRIDAY/... Models are in fairly decent agreement in terms of positions and of subsequent forecasts of synoptic scale systems. For tonight, a mid level ridge will build northward and eastward into the Ohio Valley. As this occurs, a warm front will push northeast through our area. Clouds will thicken this evening with a few showers possible for locations north of the Ohio River overnight as this area will be on the southern fringe of better moist/isentropic lift farther to the north. Lows will bottom out early, then steady out or slowly rise toward morning as southerly flow increases. Temperatures will range from the lower 40s northeast to the upper 40s southwest. On Friday, the Ohio Valley will be warm sectored in the wake of the warm front while a mid level ridge axis shifts east. Models are indicating quite a bit of low level moisture in the return low level southerly flow. This will likely result in stratus clouds early on which will likely convert over to low level cumuliform clouds during the afternoon. As a result, have kept skies mostly cloudy. Despite cloud cover, stiff southerly winds with gusts in the 20 to 30 mph range will boost highs into the mid and upper 60s. && .LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/... An unsettled pattern will be setting up over the Ohio Valley through the weekend, turning more progressive but continuing to be active going into the early part of next week. On Friday night, the ILN CWA will be within a regime of generally low pressure, stuck between highs off the southeast coast and over northern Ontario. The 500mb pattern will be amplifying in the vicinity of the Ohio Valley, even as relatively tranquil conditions are expected at the start of the long term forecast period on Friday night and Saturday morning. Well within the warm sector, heights will be rising as ridging builds into the Mississippi Valley, with a frontal boundary remaining nearly stationary across Michigan and New York. To the west, a complex stacked low pressure system will begin to take shape over the plains, moving slowly east -- near St Louis by Sunday morning, then finally clearing the Ohio Valley by Monday morning. Confidence continues to increase in the overall timing and placement with this system, though the 00Z ECMWF solution remains slightly slower than the 00Z GFS. The first part of Saturday is generally expected to be dry, outside of a few showers developing in the continued isentropic ascent. It is expected that there will be several rounds of showers (and potentially thunderstorms) along with this system, running primarily from Saturday evening through Sunday afternoon. Though the overall motion of the low will be slow, the juxtaposition of upper support, low level moisture transport, and 500mb vorticity advection will result in the possibility of multiple time periods in which showers and possibly thunderstorms will be able to develop. There continues to be strong agreement in a well- defined wave moving through the region late Saturday evening through Sunday morning, and this period has been timed out with categorical PoPs. On either side of this (Saturday afternoon and Sunday afternoon) the forcing is not as well defined, but showers and storms will be possible -- without seeing the mesoscale details, getting more specific on timing is not yet possible. Thunder has been included as a possibility on both days as well. This system will have a respectable feed of theta-e and a tight/compact 850mb- 700mb low, so forcing and moisture should be sufficient for widespread precipitation. In general, the modeling of instability has been very fickle -- changing slightly from run to run, never higher-end, and largely limited by the moist profile and poor mid- level lapse rates. Building off of that analysis, with questionable instability, the possibility for heavier rainfall or strong storms is less certain -- also owing to differences in model specifics and a pattern that is not necessarily a classic setup for either threat. Nonetheless, with decent moisture and some turning in the wind field near the low, there is at least a low-end potential to watch and refine the forecast for in the next few days. As the low weakens and moves away from the area late Sunday into Monday, the weather pattern over the Ohio Valley will become very wavy -- characterized with short wavelengths and progressive motions. A narrow ridge behind the stacked low will provide a reasonable chance for dry conditions for early Monday, but the busy 500mb pattern will mean that this dry period will not stick around for long. Though there are some timing and amplitude differences (even within the GEFS member spread) the next wave is expected to move through Monday night into early Tuesday, producing widespread precipitation across the area. However, until timing is better handled, PoPs will be kept at 50 percent for this feature. Subsidence behind the wave will likely lead to drier conditions Tuesday night into Wednesday. The continued warming trend into Saturday is likely to bring temperatures into the upper 60s to lower 70s, with warmest conditions in the southeastern CWA, where precipitation is more likely to hold off until later. Precipitation will keep the temperature forecast a little lower for Sunday, before warming again slightly on Monday -- with the air mass changing very little in general, as the main boundary will remain well north of the area. This will change after Tuesday, as the Monday night / Tuesday wave will bring a cold front into the region, beginning a slight cooling trend going into the middle of the week. Nonetheless, temperatures should still remain above normal, even on Wednesday. && .AVIATION /07Z THURSDAY THROUGH MONDAY/... High pressure will move off to our east today while a warm front organizes to our southwest and moves northeast toward the region. Mainly clear skies early this morning will give way to gradual thickening and advancing mid level clouds from the west. Easterly surface flow will veer to the southeast with some local gusts in the 15 to 20 knot range. For tonight, a mid level ridge will build northward and shift east into the Ohio Valley. As this occurs, a surface warm front will lift northeast through our region. A strengthening low level jet will focus most of its convergence and strongest moist ascent into Wisconsin and Michigan. However, models continue to hint that a few showers will still be possible, especially for the northern terminals as this region will be on the southern extent of the better WAA/lift. Clouds will gradually lower into the 6000-9000 foot range through early morning, then they will briefly lift back up to around 15000 kft once the warm front passes by. In addition, winds will increase from the south late tonight as the pressure gradient tightens between high pressure off to our east and low pressure moving into the central/southern Plains. The low level jet will become strong enough warrant a period of non convective LLWS in the terminals as we approach 06Z and then waning toward 15Z Friday. Finally, will interrogate models for the potential development of MVFR ceilings toward 12Z as low level moisture is advected north. Some models suggest ceilings in the 1500 to 2500 foot range by Friday morning. OUTLOOK...MVFR ceilings and visibilities likely Saturday night into Sunday along with a chance of thunderstorms. && .ILN WATCHES/WARNINGS/ADVISORIES... OH...Freeze Warning until 10 AM EDT this morning for OHZ077>079-081- 088. KY...Freeze Warning until 10 AM EDT this morning for KYZ089>100. IN...Freeze Warning until 10 AM EDT this morning for INZ073>075-080. && $$ SYNOPSIS...Hickman NEAR TERM...Hickman SHORT TERM...Hickman LONG TERM...Hatzos AVIATION...Hickman

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